The Los Angeles Times was one of the newspapers affected by a cyber-attack.
Photograph: Frederic Brown/AFP/Getty Images

A cyber-attack has caused printing and delivery disruptions to major US newspapers, including the Los Angeles Times, the Chicago Tribune and the Baltimore Sun.

The attack on Saturday appeared to originate outside the United States, the Los Angeles Times reported. It led to distribution delays in the Saturday edition of the Times, the Tribune, the Sun and other newspapers that share a production platform in Los Angeles.

Tribune Publishing, which owns the Chicago Tribune and the Sun, as well as the New York Daily News and Orlando Sentinel, said it first detected the malware on Friday.

The west coast editions of the Wall Street Journal and New York Times were also hit, as they are printed on the shared production platform, the Los Angeles Times said.

The Guardian view on Russia and hacking: time to tackle our vulnerabilities | Editorial

Read more

A Tribune Publishing spokeswoman, Marisa Kollias, said the virus affected back-office systems used to publish and produce “newspapers across our properties”.

“There is no evidence that customer credit card information or personally identifiable information has been compromised,” Kollias said.

Most San Diego Union-Tribune subscribers were without a newspaper on Saturday as the virus infected the company’s business systems and hobbled its ability to publish, the paper’s editor and publisher, Jeff Light, wrote on its website.

A spokeswoman for the Department of Homeland Security said it was studying the situation. “We are aware of reports of a potential cyber incident affecting several news outlets, and are working with our government and industry partners to better understand the situation,” said DHS spokeswoman Katie Waldman.

Representatives of the Federal Bureau of Investigation were not available for comment.